The present invention relates generally to an organic EL (electroluminescent) device using an organic compound, and more specifically to an improvement in or relating to an adhesive agent for fixing a sealing plate in place to protect an organic EL structure stacked on a substrate.
In recent years, organic EL devices have been under intensive investigation. One such device is basically built up of a thin film form of hole transporting material such as triphenyldiamine (TPD) deposited by evaporation on a hole injecting electrode, a light emitting layer of fluorescent material such as an aluminum quinolinol complex (Alq.sup.3) laminated thereon, and a metal (electron injecting) electrode of a metal having a low work function such as Mg and formed on the light emitting layer. This organic EL device now attracts attentions because a very high luminance ranging from several hundreds to tens of thousands cd/m.sup.2 can be achieved with a voltage of approximately 10 V.
A grave problem with an organic EL device is that it is acutely sensitive to moisture. Exposure of the organic EL device to moisture, for instance, causes a light emitting layer to peel off electrode layers, or materials forming part thereof to degenerate. This results in another problem that non-light emission spots called dark spots occur or any consistent light emission cannot be kept.
One approach known to solve this problem is to fix an airtight case, a sealing layer or the like closely on a substrate to cover an organic EL multilayer structure, thereby shielding it from the outside, as typically disclosed in JP-A's 5-36475, 5-89959 and 7-169567.
Even with the provision of such a sealing layer, however, several problems still arise; as driving time goes by, the light emission luminance decreases or the dark spots occur. If the dark spots become large, then the device will deteriorate and, in the worst case, the device will be unable to work.